The present invention relates to adjustable vehicle seats which include an adjustable headrest.
The adjustable vehicle seat headrest was introduced, at least in part, as a safety device to support the head of an occupant during a vehicle crash. To function properly the position of the headrest should be adjusted to the height of the individual occupying the seat to which the headrest is mounted. Often, in modern vehicles, the various possible movements of the seat have been motorized and are readily adjusted by the seat occupant. However, although the occupant is strongly motivated to adjust the seat for comfort, the position of the headrest often does not contribute to an immediate sense of comfort and therefore is at times not adjusted to conform to the occupant""s height. Thus the headrest may be adjusted to improve perceived visibility, or simply left in the position in which it is found.
To maximize the benefits to be gained from a headrest, it is desirable that the headrest always be properly positioned. Therefore, a system for adjusting the headrest which does not depend on the occupant directly adjusting the headrest is desirable.
The vehicle seat of this invention is mounted for motorized adjustment with respect to the steering wheel, or front of the vehicle, to accommodate seat occupants of varying heights. The vehicle seat has mounted thereto a headrest which is also mounted for motorized adjustment so that the position of the headrest may be adjusted to accommodate seat occupants of varying heights. The seat position drive mechanism, and the headrest drive mechanism are designed to be driven together so that the seat occupant, when adjusting the seat position, will simultaneously adjust the headrest height by an amount proportional to the position to which the seat is adjusted. The headrest height and seat position can be driven together by the simple expedient of connecting the headrest drive motor and the seat drive motor to a single control switch. Because the headrest has a smaller total distance of travel as compared to the vehicle seat, the headrest motor may drive a thread with a smaller pitch. Another approach for controlling the relative movement of the headrest with respect to the vehicle seat is to use pulse width modulation of the electrical power supplied by the common switch, thus reducing the effective speed of the headrest motor. A further approach is to design the motors to incorporate gears or other mechanisms whereby the headrest motor causes the headrest screw to rotate at a slower speed than the seat positioning screw.
It is a feature of the present invention to provide a vehicle seat where independent adjustment of headrest height is not required.
It is another feature of the present invention to provide a vehicle seat where the headrest height and seat position are linked together.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.